An integrated type solar cell having a plurality of photoelectric conversion elements integrated is known as a solar cell. Conventionally, this type of integrated solar cell mainly has an external profile of substantially a rectangle such as an oblong figure or square. In contrast, the planar shape of the roof of a house includes various shapes such as a triangle and trapezoid in addition to the rectangle such as an oblong figure or square. When an integrated type solar cell is to be installed on the roof of a house, there may be a blank region on the roof where the integrated type solar cell cannot be installed depending upon the planar shape of the roof. There was a problem that the area of the roof cannot be used effectively. There was also a problem that the roof is not aesthetically acceptable.
In order to solve such problems by installing an integrated type solar cell at a region on the roof where installation of an integrated type solar cell is not allowed due to the planar shape of the roof, Patent Documents 1-7 set forth below propose an integrated type solar cell taking a triangle or trapezoid for the external profile of the integrated type solar cell.
Patent Document 1: Japanese Patent Laying-Open No. 10-12911
Patent Document 2: Japanese Patent Laying-Open No. 10-65198
Patent Document 3: Japanese Patent Laying-Open No. 2001-111084
Patent Document 4: Japanese Patent Laying-Open No. 10-74964
Patent Document 5: Japanese Patent Laying-Open No. 2001-203380
Patent Document 6: Japanese Patent Laying-Open No. 2000-208804
Patent Document 7: Japanese Patent Laying-Open No. 2003-243688
However, conventional integrated type solar cells had problems as will be set forth below. Patent Documents 1 and 7 propose an integrated solar cell having crystalline cells aligned as an integrated type solar cell. There was a problem that connection between crystalline cells is rendered complex. In Patent Document 2, connection between cells constituting an integrated type solar cell is effected by a conductive adhesive or the like applied at a predetermined end of the cell. There was a problem that the connection step thereof is rendered complicated.
Patent Document 6 had the connection between cells constituting an integrated type solar cell effected using electrical connection. Therefore, there was a problem that the connection process is rendered complex. According to Patent Document 3, connection between cells constituting an integrated type solar cell is effected via a through hole and a current collector aperture. There was a problem that associated steps are rendered tedious.
According to Patent Document 4, the vertex of each of the plurality of cells constituting an integrated type solar cell is gathered at one site. Therefore, there was a problem that the working process is rendered complex and the working precision degraded. Further, according to Patent Document 5, the difference in width (pitch) between a cell of large width and a cell of small width regarding cells constituting an integrated type solar cell is so great that it is disadvantageous from the standpoint of photoelectric conversion property as an integrated type solar cell. Further, there was a problem that the working process is rendered complex.
Thus, conventional integrated type solar cells had problems related to connection between the cells (photoelectric conversion elements) constituting the integrated type solar cell and problems related to the shape of the cells.
The example embodiment presented herein is directed to solving such problems seen in conventional integrated type solar cells. One aspect is to provide an integrated type solar cell that allows connection between photoelectric conversion elements without difficulty and capable of efficient photoelectric conversion. Another aspect is to provide a fabrication method of such a solar cell.
A solar cell according to the present embodiment corresponds to a solar cell including a plurality of photoelectric conversion elements. The solar cell includes a transparent insulation substrate, a prescribed layer, and a plurality of photoelectric conversion elements. The transparent insulation substrate has a predetermined external profile. The prescribed layer is formed on a main surface of the transparent insulation substrate, constituting photoelectric conversion elements. The plurality of photoelectric conversion elements are formed by delimiting the prescribed layer with a plurality of isolation line regions spaced apart from each other, extending in one direction and exposing the surface of the transparent insulation substrate, and a plurality of connection line regions spaced apart from each other, extending in another direction crossing the one direction. At each of a plurality of regions located between the isolation line regions, a string of photoelectric conversion elements electrically connected in series by connection line regions is formed. By the string formed in each of the regions located between the plurality of isolation line regions, an integrated string having one string electrically connected with a further string is formed in plurality. The plurality of integrated strings are electrically connected in parallel.
According to the configuration set forth above, electrical connection of a plurality of photoelectric conversion elements can be effected readily on a transparent insulation substrate by the connection line regions and isolation line regions formed at the transparent insulation substrate, without the usage of an additional member. By delimiting each photoelectric conversion element through an isolation line region formed extending in one direction and a connection line region extending in another direction crossing the one direction, the shape as well as the area of each photoelectric conversion element will become identical. Therefore, variation in the photoelectric conversion property is eliminated, allowing output efficiently.
In order to dispose such a solar cell in accordance with the planar shape of the roof, the outer circumference of the transparent insulation substrate is preferably constituted of at least three outer edges, respectively extending linear, i.e. a first outer edge, and second and third outer edges not parallel to the first outer edge.
In order to eliminate potential difference between the plurality of integrated strings, it is preferable to set the sum of the number of photoelectric conversion elements in one string and the number of photoelectric conversion elements in a further string identical with each other.
In the case where the external profile of the transparent insulation substrate is a triangle formed of a first outer edge, a second outer edge, and a third outer edge, preferably each of the isolation line regions is arranged substantially parallel to the first outer edge, and each of the connection line regions is arranged substantially parallel to the second outer edge. In this case, the external profile of the photoelectric conversion element is a rectangle or a parallelogram.
In order to eliminate any region that does not contribute to power generation at the third outer edge side in the case where the transparent insulation substrate has a triangular external profile, preferably an additional photoelectric conversion element electrically connected to a photoelectric conversion element by respective corresponding connection line regions and of a trapezoidal shape with an area identical to the area of the photoelectric conversion element is formed at each region located between the isolation line regions at the third outer edge side of the transparent insulation substrate.
Furthermore, in order to better accommodate various planar shapes of the roof, there is provided an additional transparent insulation substrate having an external profile of a quadrilateral, and a plurality of additional photoelectric conversion elements formed at the additional transparent insulation substrate. By electrically connecting the plurality of photoelectric conversion elements formed at the transparent insulation substrate and the additional photoelectric conversion elements formed at the additional transparent insulation substrate and arranging the transparent insulation substrate and the additional transparent insulation substrate in parallel, an external profile corresponding to a trapezoid may be obtained.
For each of the photoelectric conversion element to take a triangular external profile in the case where the external profile of the transparent insulation substrate is a triangle, there may be provided a plurality of additional connection line regions spaced apart from each other, and substantially parallel to the third outer edge.
In order to prevent any unintentional short-circuiting between a connection line and another connection line, the isolation line region is preferably formed having a width eliminating the region where a connection line region crosses an additional connection line region and to expose the surface of the transparent insulation substrate, or formed as a pair of regions to expose the surface of the transparent insulation substrate. A region where a connection line region crosses an additional connection line region is located between one and the other of the regions of a pair.
The one string and the further string are preferably electrically connected on the transparent insulation substrate by the patterning of the isolation line regions. Accordingly, connection between strings can be effected readily and reliably without an additional interconnection.
Respective terminals for electrically connecting one string with a further string are preferably connected to each other at the same outer edge side of the transparent insulation substrate by arranging the one string and the further string such that the direction of current flowing through one string is opposite to the direction of current flowing through the further string at each of the plurality of integrated strings. Accordingly, it is not necessary to route the interconnection. Furthermore, crossing between interconnections is eliminated. As used herein, a triangle, a quadrilateral, and a trapezoid are not intended to refer to the strict mathematical geometry, but instead a figure which can be recognized at a glance.
A fabrication method of a solar cell according to the present embodiment includes the steps of: forming a first conductive layer on a main surface of a transparent insulation substrate; forming a photoelectric conversion layer on the first conductive layer; forming a second conductive layer on the photoelectric conversion layer; forming predetermined connection line regions spaced apart from each other and extending in one direction by scribing each of the first conductive layer, photoelectric conversion layer and second conductive layer; and forming isolation line regions spaced apart from each other, extending in another direction crossing the one direction, and exposing the surface of the transparent insulation substrate at the second conductive layer, photoelectric conversion layer, and first conductive layer. In the step of forming connection line regions, the connection line regions are formed to provide a plurality of photoelectric conversion elements including a first conductive layer, photoelectric conversion layer, and second conductive layer, and to constitute a string having adjacent photoelectric conversion elements connected to each other in series, at the region to be located between the isolation line regions. In the step of forming isolation line regions, the isolation line regions form an integrated string electrically connecting one string with a further string in plurality, by the string formed at each of the regions to be located between the isolation line regions, and the plurality of integrated strings are electrically connected in parallel.
By the method set forth above, electrical connection of a plurality of photoelectric conversion elements can be effected readily on a transparent insulation substrate by connection line regions and isolation line regions formed at the transparent insulation substrate. Furthermore, by the delimitation of each photoelectric conversion element through the isolation line regions and connection line regions, each photoelectric conversion element will have the same profile and the same area. Thus, variation in the photoelectric conversion property is eliminated to allow output efficiently.